Second the Pro Arte strings. Classical strings can normally be purchased in seperate sets for the wound 4, 5, and 6th strings, normally referred to as bass sets. Get the Pro Arte basses and a set of fluorocarbon trebles. If you're concerned with the ability of your instrument to take higher tensions then just purchase the sets in medium tension. Sets are also sold in "hard" tension and you may want to use the lighter tension mediums.

This particular guitar doesn't have a truss rod so I'll stick with medium tension strings. Actually the old strings that are on it don't sound too bad. Plenty of volume on the bass strings and the treble strings are a little more subdued. Is this typical of a cedar topped classical?